Explosionproof hand lamp



N. A. TQRNBLO/ EXPLOSIONPROOF HAND LAMPl Filed Aug.

Patented Jan. 14, 1941 UNITED STATES r'rsnr errno EXPLosroNrRooF HANnLsMr Nils A. Tornblom, Chicago, Ill., assigner to Appleton Electric Company, a corporation of Illinois The object of the present invention is to produce a simple and novel electric lamp connected to one end of a cable and adapted to be held in Vthe hand to provide illumination in comparatively inaccessible places and elsewhere.

Viewed in one of its aspects, the present invention may be said to have for its object to produce a hand lamp that shall be compact, of very sturdy construction so as to be capable of withstanding rough usage, and have its lighting bulb so housed that there is no danger of igniting combustible gases in the surrounding atmosphere in the event of breakage of the bulb unless the lamp structure as a whole is destroyed.

'Ihe Various features of novelty whereby my invention is characterized will hereinafter be pointed out with particularity in the claims; but, for a full understanding of my invention and of its objects and advantages, reference may be had to the following detailed description taken in connection with the accompanying drawing, where- 1n:

Figure 1 is a side elevation of a lamp embodying the present invention; Fig. 2' is a central longitudinal section through the lamp, the extreme end portions of the lamp being broken olf; Figs. 3 and 4 are sections taken respectively on line 3-3 and line 4-4 of Fig. 2; and Fig. 5 is a section on line 5--5 of Fig. 4, showing only a fragment of the lamp.

Referring tc the drawing, I represents a cage, comprising two short sleeve-like end members 2 and 3 connected by longitudinal bars 4, spaced apart from each other. The sleeve members 2 and 3 are internally screw threaded for a considerable distance inwardly from their outer ends, as indicated at 5. Within this cage is a thickwalled glass tube 6 sumciently long to permit both of its ends to extend for some distance into the inner ends of the two sleeves. In actual practice I have found it advisable to give the wall of this tube a thickness of about threeeighths of an inch. Screwed into the members 2' and 3 are ring nuts 'I which serve to hold the glass tube in place. These nuts are preferably recessed on their inner faces, over a. diameter equal to the external diameter of the glass tube, so that the ends of the tube may fit into these recesses and cause the tube to vbe accurately centered. Within the recesses in each nut are two fiat rings or Washers 8 and 9, preferably composed of soft aluminum. The end faces of the glass tube are preferably ground so as to be fiat and make good contact over their entire areas with the rings. When the ring nuts are 4tightened, the metal of the rings or washers flows -sheet metal, having a plurality of ngers II struck Y received in the notches.

sufciently toseal the joints between the nuts and the glass tube.

The outer end of the sleeve 2 is closed by a cap o-r head III screwed into the same, while a hollow handle II is screwed into the outer end of the 5' sleeve 3. The parts are so proportioned that there are enough screw threads between each ring nut and the corresponding sleeve and between the members I0 and I I and the sleeves with which they respectively cooperate, to insure against ignition of a. surrounding combustible atmosphere due to leakage through these joints in the event of the creation of a spark or flame within the cage and its hollow handle.

'Ihe handle II, which is in the form of a long "15j sleeve, contains a thick transverse partition I2 near its inner end. Screwed into and extending in opposite directions fromthe partition I2 is a receptacle I4, formed of suitable insulating material. Supported by the receptacle I4 is a long, slender electric light bulb I5 that extends through the cage to the farther end of the latter and there engages a suitable centering device that may conveniently take the form of a disc I6 of resilient T25 therefrom and engaging with the rounded free end of the bulb. It should be noted that the partition I2 is thick enough to provide the requisite number of screwthreads between the same and the receptacle to insure against propagation of flame on one side of the partition in the event that flame is created on the opposite side. The terminals by which the supply wires are connected to the receptacle are conveniently tubular members I8 that are molded into the body of the receptacle in the process of manufacturing'the latter. The terminal end of the body of the receptacle is cut away so fas to leave a mere shelf I9 underlying and parallel with the two terminals. Resting upon this shelf is a block 20 of insulating material that may conveniently be held in place by a screw 2I extending down through the same and into the shelf. The block 20 has two deep notches 22' cut into the same from the bottom edge; the notches being at least as wide as the diameters of the terminals I8, and being so spaced that when the block is lowered upon the shelf, the terminals are 'Thus the block insulates the projecting portions of the terminals I 8 from each other and from the surrounding handleo housing.v It will be seen in Fig. 2 that the terminals I8 do not extend clear through the block I 20 but stop short a substantial distance inwardly from the outer or rear face of the latter. This permits the insulation on the conductors leading to the terminals to enter the notches or pockets in the block and thus leave no metal exposed in a manner to make a short circuit possible. The interior of the handle housing is preferably lined with a sleeve 24 of insulating material which may be simply paper, in the zone of the insulating block 2U and for some distance outwardly beyond the same.

The handle housing is cut away, as indicated in Figs. 4 and 5, to give access to the interior in the vicinity of the insulating block which extends up into or through this opening. It will be seen that upon removing the screw 2l, the insulating block may be lifted out of the handle and expose the terminals I8; thereby facilitating the connection of the leads to the terminals. The lining 24 is also cut away in registration with those portions of the opening or window in the handle housing which it spans.

In order to close the opening in the handle housing,vI have provided the housing with a detachable casing in the form of a cylindrical sleeve 25 that may be slipped upon the same and be held in place by means of a screw 28, or otherwise.

After the receptacle I4 has been properly assembled in the handle housing, it is held against accidental rotation by means of a pin 2l inserted in the wall of the handle housing and extending inwardly into a notch or hole 28 in the shelf I9.

The cable containing conductors to be connected to the terminals I8 and to a ground terminal 29 within the handle may be led into the free end of the handle through any suitable connector 30, preferably of the type containing a soft rubber sleeve 3| that provides a seal around the cable at the point where it enters the handle.

fio

It is desirable that the lamp be provided with a reflector. By fitting the ends of the glass tube 6 into the recesses in the ring nuts 1, an annular space is provided between the glass tube and the surrounding cage members into which may be set a curved reflector plate 32 that is made approximately as long as the distance between the two ring nuts when the latter are tightened, but preferably a little shorter, so that it will not interfere with the proper adjustment of the nuts and yet will cause both of its ends to be entered for some distance into the sleeve members 2 and 3.

It will be seen that by making the wall of the glass tube E quite thick, it is not only provided with great mechanical strength to insure against breakage, but its end faces may be of suicient radial widths to comply with the requirements of re underwriting associations which regard a good contact between flat faces over a width of three-eighths of an inch as constituting an explosionproof joint. In the same way, by making the screw threaded portions of the sleeve-like ends of the cage sufficiently long, the number of screw threads embodied in each joint is large enough to comply with the requirements to make screw thread jointsv explosionproof. This is also true with respect to the joint between the receptacle I4 and the thick partition I2. Consequently, when the parts are properly assembled, the lamp as a whole is very rugged and, for all practical purposes, explosionproof.

It will also be seen that by providing the hollow handle with an opening or Window, the conductors contained in the cable entering the end of the handle can be easily connected to and disconnected from the several terminals and the connections be then protected against tampering when the sleeve or cover is slipped on the handle and secured in place.

While I have illustrated and described with particularity only a single preferred form of my invention, I do not desire to be limited to the exact structural details thus illustrated and described, but intend to cover all forms and arrangements Which come within the definitions of my invention constituting the appended claims.

I claim:

1. In combination, an open-work cage having sleeve-like ends, a thick-walled glass tube considerably shorter than the cage arranged within the same, ring nuts screwed into said sleeve-like ends and serving to clamp the tube between them, the end faces of said tube being ground smooth, sealing means between the said end faces and the nuts including metal washers having smooth faces engaged with said end faces of the tube, an imperforate cap screwed into one of said sleeve-like ends outwardly from the corresponding ring nut, an imperforate holder for a receptacle screwed into the other of said sleeve-like ends, the radial widths of said tube end faces and the number of threads between the sleeve-like ends of the cage and each of the members screwed into the same being such that no flame can pass through the joints made thereby.

2. In combination, an open-work cage having sleeve-like ends, a vthick-walled glass tube considerably shorter than the cage arranged within the same, ring nuts screwed into said sleeve-like ends and serving to clamp the tube between them, the end faces of said tube being ground smooth, sealing means between the said end faces and the nuts including metal washers having smooth faces engaged with said end faces of the tube, a

cap screwed into one of said sleeve-like ends outwardly from the corresponding ring nut, a holder for a receptacle screwed into the other of said sleeve-like ends, the radial widths of said tube end faces and the number of threads between the sleeve-like ends of the cage and each of the members screwed into the same being such that no flame can pass through the joints made thereby, lingers onV said cap for engaging with the end of a light bulb mounted in the receptacle and holding said bulb centered.

3. In combination, an open-work cage having sleeve-like ends, a thick-walled glass tube considerably shorter than the cake arranged within the same, ring nuts screwed into the said sleevelike ends and clamping the tube between them, a cap screwed into one of said ends, a hollow handle screwed into the other of said ends, said handle having a thick internal transverse partition at some distance from the cage, a receptacle -v vscrewed into and projecting from both sides of the said partition, said receptacle having a socket for a light bulb on the end at the cage, and terminals molded into the body of the receptacle and exposed within the handle on the side of the partition remote from the cage.

4. A shield unit for a lamp bulb comprising anopen-work cage having like sleeve-like end members, a glass tube considerably shorter than the cage and somewhat smaller in external diameter than the internal diameter of said sleevelike members arranged within the cage, ring nuts screwed into the sleeve-like members and clamping the tube between them, said nuts having recesses into which the ends of the tube fit, and a loose curved reflector arranged between the tube and the surrounding cage and extending from one of said nuts to the other.

5. In combination, an open-Workcage having sleeve-like ends, a thick-walled glass tube consderably shorter than the cage arranged within the same, ring nuts screwed into the said sleevelike ends and clamping the tube between them, a

cap screwed into one of said ends, a hollow and projecting from both sides of the said partition, the cage end of the receptacle being adapted to receive a light bulb, terminals molded into the body of the receptacle and exposed within the handle on the side of the partition remote from the cage, the receptacle body having a shelf projecting therefrom on one side of and beyond the said terminals, and a block of insulating material resting on and detachably secured to said shelf, said blocking having recesses for the terminals.

6. In combination, an open-work cage having sleeve-like ends, a thick-walled glass tube considerably shorter than the cage arranged Within the same, ring nuts screwed into the saidl sleevelike ends and clamping the tube between them, a cap screwed into one of said ends, a hollow handle screwed into the other of said ends, said handle having a thick internal transverse partition at ysome distance from the cage, a receptacle having a body of insulating material screwed into and projecting from both sides of the said partition, the cage end of the receptacle being 'adapted to receive a light bulb, terminals molded into the body of the receptacle and exposed within the handle on the side of the partition remote from the cage, the receptacle body having a shelf projecting therefrom on one side of and beyond the said terminals, and a block of insulating material resting on and detachably secured to said shelf, said block having recesses for the terminals, there being an opening in the side of the handle through which the said block of insulating material may be removed o-r inserted.

NILS A. TORNBLOM. 

